In electronic systems there is a common need to convert analog signals into a form suitable for use by a processor or controller. An analog-to-digital converter (A/D or ADC) is a circuit that converts an analog signal into one or more digital numbers representing the magnitude(s) of the analog signal. In the case of a time-varying input signal, an ADC periodically samples the input signal and generates a series of digital values.
If the input signal has a wide dynamic range (large range of amplitudes) an automatic-gain-control amplifier (AGC) may be used to keep the input to the ADC below the full-scale limit. The gain of the AGC may be controlled by the digital output of the ADC. However, the loop speed for adjusting gain is then dependent on the overall conversion time, and if the input signal also has a high bandwidth the ADC may not be able to track the input signal. An alternative for wide dynamic range input signals is to make a wide range ADC with many bits or digits in each digital output. However, power consumption and complexity of an ADC typically increases with the number of bits in the output. In addition, in many cases, the number of bits per sample needed for accuracy may be much less than the number of bits needed to satisfy the dynamic range.
There is an ongoing need for an ADC with wide dynamic range but with lower complexity and reduced power requirements compared to simply increasing the number of bits.